The present invention relates to hydraulic power steering systems and more specifically relates to follow-up circuitry for such systems.
It is desirable to have steering systems which provide fine steering control for minor steering corrections, especially at high speeds, while providing steering control for making sharp turns without requiring a relatively large number of turns of the steering wheel from lock-to-lock.
A known steering system, which embodies a metering pump for producing a steering input signal across a steering valve and a follow-up cylinder for producing a follow-up signal to nullify the input signal once a desired turn is made, has the characteristic of providing fine steering control, however it does not permit sharp turns to be made without excessive steering wheel motion. While the number of turns lock-to-lock of this known system is determined by the relative size of the metering pump to the follow-up cylinder displacement and can therefore be decreased by increasing the metering pump size or decreasing the follow-up cylinder displacement, such changes in size would result in a loss of fine steering control.